Fixes looping over all itemtypes

Author: TheLimeGlass

src/main/java/ch/njol/skript/aliases/ItemType.java

@@ -541,7 +541,7 @@ public boolean hasNext() {
 
 			@Override
 			public ItemStack next() {
-				if (nextItem == null)
+				if (!hasNext())
 					throw new NoSuchElementException();
 				ItemStack result = nextItem;
 				nextItem = null;